Nah, unfortunately NAT doesn't really do a good job of hiding what the source machine is. People have used this to analyse how many machines are behind a NAT wi

Nah, unfortunately NAT doesn't really do a good job of hiding what the source machine is. People have used this to analyse how many machines are behind a NAT with very clear patterns emerging based on TCP/IP timestamps as well as the sequence numbers (which are sequential in most OS's). The bigger concern is the fact that you apparently have access to the data being sent/to from an IP address and can thus sniff the data in the first place. Whether that be a NAT'ed or IPv6 IP address.